Lapping tool



Nov. 8, 1955 Filed Aug. 9, 1954 G. W. HOLMES LAPPING TOOL IN VEN TOR.

GEORGE W HOLMES (9m, MA 0 M, 71ml;

ATTYS United States Patent LAPPING TOOL George W. Holmes, Columbus, Ohio ApplicationtAugust 9, 1954, Serial No. 448,531

6 Claims. (Cl. 51-204) This invention relates to lapping tools and pertains particularly to a tool for lapping internal grooves formed in valve members or other machine parts.

One principal object of the invention is to provide an improved tool for lapping relatively inaccessible internal annular grooves formed along a bore in a workpiece.

A further object is to provide an improved tool which is particularly well adapted for lapping the end faces of internal annular grooves in order to bring the end faces to their finished dimensions with a high order of precision.

t is another object of the invention to provide an improved lapping tool which may readily be mounted and demounted from a bore in a workpiece.

Further objects and advantages of the invention will appear from the following description, taken with the accompanying drawing, in which:

Figure 1 is an exploded view of a lapping tool constituting a purely illustrative embodiment of the invention.

Figure 2 is an enlarged fragmentary longitudinal sectional view of the tool shown mounted in a workpiece, the view being taken generally along a line 22 of Figure 3.

'Figure 3 is a cross sectional view taken generally along a line 33 in Figure 2.

' Figure 4 is a perspective view of a segmental lapping element employed in the tool of Figure 1.

Considered in greater detail, the drawing illustrates a lapping tool adapted to lap end faces 11 of an internal annular groove 12 formed along a bore 14 in a work piece 15. It will be understood, however, that the lapping tool may be employed for a variety of other lapping operations. The illustrated workpiece 15 consists of a body for a hydraulic control valve utilized in operating control surfaces on high-speed aircraft. When the valve body. 15 is installed in the valve, the groove 12 cooperates with a valve spool (not shown) which is movable into and out of registration with the groove so as to control the flow of hydraulic fluid through a port 17 communicating with the groove 12. In order that all of the hydraulic control valves may operate in the same manner and thus facilitate the piloting of the aircraft, it is necessary to locate the end faces 11 with a high order of precision. To this end it has been found highly desirable to finish the end faces 11 by a hand lapping operation.

As illustrated, the lapping tool 10 comprises a plurality of lapping segments 18, three of the segments being employed in this instance. The segments 18 are generally cylindrically curved and are provided with centrally located ribs 19 adapted to be inserted into the internal annular groove 12. The peripheral length of the segments is made such that they may be inserted through the bore 14 into the groove 12 with the aid of a suitable hand tool such as a magnetized rod (not shown). It will be understood that a suitable abrasive lapping compound is applied to the segments 18 before they are inice serted into the groove 12. Flat annular end faces 20 are formed on the segments 18 to lap the end faces 11 of the groove 12.

To maintain the ribs 19 square with the groove 12, the lapping segments 18 are formed with arcuate guide portions 22 at their opposite ends. Cylindrically curved outer surfaces 23 are formed on the guide portions vfor sliding engagement with the bore 14. Each of the lapping segments 18 is also formed with a continuous internal cylindrically curved guiding surface 24.

The lapping segments 18 are supported in the workpiece 15 by means of a two-piece arbor 26 having first and second sections 27 and 28 adapted to be connected together with the lapping segments mounted therebetween. In the illustrated construction, the first arbor section 27 is provided with a cylindrical portion 29 adapted to be supported in the bore 14 with a sliding fit. Extending from one end of the cylindrical portion 29 is a stem 30 of reduced diameter for insertion within the cylindrical inner surfaces 24 of the lapping segments 18. A shoulder 31 is formed between the cylindrical portions 29 and 30 for engagement with end faces 32 on the lapping segments.

At its outer end the stem 30 is provided with a tapered portion 34 to earn the segments 18 outwardly into the groove 12 when the arbor section 27 is inserted into the bore 14. A screw 35 extends axially from the stem 30 for engagement with an internally threaded bore 36 formed in the second arbor section 28. An end face 38 is formed on the second section 28 for engagement with the end faces 32 of the segments 18 in opposition to the shoulder 31.

In operation, a suitable abrasive lapping compound is applied to the lapping segments 18 or to the end surfaces 11 to be lapped. The lapping segments are inserted through the bore 14 into the groove 12. Next, the arbor sections 27 and 28 are inserted into the opposite ends of the bore 14. The stem 30 on the arbor section 27 is thereby moved within the inner surfaces 24 of the lapping segments so as to hold the segments in the groove 12 against inward movement. The screw 35 is engaged with the threaded bore 36 so as to clamp the segments between the end surfaces 32 and 38 on the arbor sections 27 and 28. The end faces 11 may then be lapped simply by rotating either of the arbor sections manually while applying pressure between the lapping faces 20 of the segments and the end faces 11 of the groove 12. In this way the surfaces 11 may be finished with a high order of precision. The lapping tool 18 may be removed from the workpiece 15 simply by disconnecting the arbor sections 27 and 28 and withdrawing the segments 18 through the bore 14. The facility with which this may be done is an important feature of the lapping tool since the tool must be removed frequently in order that the groove 12 may be inspected and gauged.

Various modifications, equivalents and alternative constructions may be employed without departing from the true spirit and scope of the invention as set forth in the foregoing description and the accompanying drawing, and as defined in the following claims.

I claim:

1. A lapping tool for lapping end faces of an internal annular groove in a bore formed in a workpiece, said tool comprising a plurality of arcuate lapping segments adapted to be inserted into the groove through the bore, each of said lapping segments having a central peripherally extending rib receivable in the groove and a pair of reduced arcuate guide portions extending from opposite sides of said rib and receivable in the bore, said segments having respective arcuate cylindrically concave inner surfaces, a first arbor member having an outer surface slidably receivable in the bore and having a reduced end portion receivable within said inner surfaces of said segments to hold the segments outward, said first arbor member having a shoulder defined thereon between said outer surface and said end portion for engaging one end of each of said segments, a second arbor member having an end face for engaging the opposite end of each of said segments, a screw projecting axially from one of said arbor members, and an axially extending internally threaded bore formed in the other of said arbor members for receiving said screw to clamp said segments between said arbor members.

2. A lapping tool for lapping an annular internal groove in a bore formed in a workpiece, said tool comprising a plurality of arcuate lapping segments adapted to be inserted into the groove through the bore, said segments having respective arcuate cylindrically concave inner surfaces, and arbor means having a cylindrical outer surface slidably receivable in the bore, said arbor means having a cylindrical portion of reduced diameter engageable with said inner surfaces for supporting said segments.

3. A lapping tool for lapping an internal annular groove in a bore formed in a workpiece, said tool com prising a plurality of arcuate lapping segments adapted to be inserted into the groove through the bore, each of said lapping segments having a central peripherally extending rib receivable in the groove and a pair of reduced arcuate guide portions extending from opposite sides of said rib and receivable in the bore, and a pair of detachably interengageable arbor members for supporting said segments.

4. A lapping tool for lapping an internal groove in a bore formed in a workpiece, comprising a plurality of arcuate lapping segments adapted to be inserted into the groove through the bore, each of said lapping segments having a central peripherally extending rib receivable in the groove and a pair of reduced arcuate guide portions extending from opposite sides of said rib and receivable in the bore, said segments having respective arcuate cylindrically concave inner surfaces, a first arbor member having an outer surface slidably receivable in the bore and having a reduced end portion receivable within said inner surfaces of said segments to hold the segments outward, said first arbor member having a shoulder defined thereon between said outer surface and said end portion for engaging one end of each of said segments, a second arbor member having an end face for engaging the opposite end of each of said segments, and means for detachably interconnecting said arbor members.

5. A lapping tool for lapping end faces of an internal groove formed in a bore in a workpiece, comprising a plurality of cylindrically curved lapping segements receivable in the internal groove in peripherally spaced relation, said segments being dimensioned for insertion into the groove through the bore, a two-part arbor for supporting and actuating said lapping segments, said arbor comprising first and second shafts receivable in the bore, said first shaft having a reduced guide stem extending axially from one end thereof to hold said segments in the groove against inward movement, said first shaft having a shoulder thereon for engaging one end of each of said segments, said second shaft having an end face thereon for engaging the opposite end of each of said segments, and means for detachably interconnccting said shafts.

6. A lapping tool for lapping end faces of an internal annular groove formed in a bore in a workpiece, said tool comprising a plurality of lapping segments receivable in the internal groove in peripherally spaced relation, each of said lapping segments having a central peripherally extending lapping rib thereon of a conformation corresponding to the conformation of the groove to lap a surface thereof by peripheral movement of said segment, each of said segments having reduced arcuate guide portions extending longitudinally from opposite ends of said lapping rib and receivable in the bore, each of said lapping segments having a substantially continuous arcuate cylindrically concave under surface, said segments being adapted to be inserted into the groove through the bore, a two-part arbor for supporting and actuating said lapping segments, said arbor comprising first and second shafts receivable in the bore, said first shaft having a reduced generally cylindrical guide stem extending axially from one end thereof and engageable with said under surfaces of said lapping segments to hold said segments in the groove against inward movement, said stem having a tapered outer end portion for camrning said segments outwardly into the groove, said first shaft having a shoulder thereon for engaging one end of each of said segments, said second shaft having an end face thereon for engaging the opposite end of each of said segments, a screw extending axially from the end of said stem, and an axial internally threaded bore formed in said second shaft for receiving said screw to clamp said segments between said first and second shafts.

References Cited in the file of this patent UNITED STATES PATENTS 639,701 Basener Dec. 26, 1899 

